Population ageing and mortality during 1990-2017: A global decomposition analysis

Abstract

Background: As the number of older people globally increases, health systems need to be reformed to meet the growing need for medical resources. A few previous studies reported varying health impacts of population ageing, but they focused only on limited countries and diseases. We comprehensively quantify the impact of population ageing on mortality for 195 countries/territories and 169 causes of death.

Methods and findings: Using data from the Global Burden of Disease Study 2017 (GBD 2017), this study derived the total number of deaths and population size for each year from 1990 to 2017. A decomposition method was used to attribute changes in total deaths to population growth, population ageing, and mortality change between 1990 and each subsequent year from 1991 through 2017, for 195 countries/territories and for countries grouped by World Bank economic development level. For countries with increases in deaths related to population ageing, we calculated the ratio of deaths attributed to mortality change to those attributed to population ageing. The proportion of people aged 65 years and older increased globally from 6.1% to 8.8%, and the number of global deaths increased by 9 million, between 1990 and 2017. Compared to 1990, 12 million additional global deaths in 2017 were associated with population ageing, corresponding to 27.9% of total global deaths. Population ageing was associated with increases in deaths in high-, upper-middle-, and lower-middle-income countries but not in low-income countries. The proportions of deaths attributed to population ageing in 195 countries/territories ranged from -43.9% to 117.4% for males and -30.1% to 153.5% for females. The 2 largest contributions of population ageing to disease-specific deaths globally between 1990 and 2017 were for ischemic heart disease (3.2 million) and stroke (2.2 million). Population ageing was related to increases in deaths in 152 countries for males and 159 countries for females, and decreases in deaths in 43 countries for males and 36 countries for females, between 1990 and 2017. The decreases in deaths attributed to mortality change from 1990 to 2017 were more than the increases in deaths related to population ageing for the whole world, as well as in 55.3% (84/152) of countries for males and 47.8% (76/159) of countries for females where population ageing was associated with increased death burden. As the GBD 2017 does not provide variances in the estimated death numbers, we were not able to quantify uncertainty in our attribution estimates.

Conclusions: In this study, we found that population ageing was associated with substantial changes in numbers of deaths between 1990 and 2017, but the attributed proportion of deaths varied widely across country income levels, countries, and causes of death. Specific preventive and therapeutic techniques should be implemented in different countries and territories to address the growing health needs related to population ageing, especially targeting the diseases associated with the largest increase in number of deaths in the elderly.

Fig 1. Global death changes associated with population ageing, population growth, and mortality change from 1990 to 2017.

The decomposition was conducted using the number of deaths in 1990 as the reference for each year.

Fig 2. Proportion of deaths associated with population ageing globally and by country income category, 1990–2017.

(A) Male; (B) female. Decomposition analysis was conducted using the number of deaths in 1990 as the reference. The attributed proportion of deaths was calculated as the number of deaths attributed to population ageing divided by total deaths in 1990 × 100%.

Fig 3. Proportion of deaths associated with population ageing between 1990 and 2017 in 195 countries and territories.

(A) Male; (B) female. The attributed proportion was calculated as the change in total deaths attributed to population ageing between 1990 and 2017 divided by total deaths in 1990 × 100%. Countries and territories with negative attributed proportions were treated as a single category. Countries with positive attributed proportions were classified into 5 categories according to quintiles of positive attributed proportions. The maps were drawn using the R package “maps,” which was based on the data from the Natural Earth project.

Fig 4. Ratio between total deaths attributed to change in mortality rate and total deaths associated with population ageing between 1990 and 2017.

(A) Male; (B) female. The ratio was calculated as the change in total deaths attributed to change in mortality rate divided by that associated with population ageing. Blue signifies countries and territories for which the decrease in total deaths attributed to changes in mortality was more than the increase attributed to population ageing between 1990 and 2017. Red signifies countries and territories for which the decrease in total deaths attributed to changes in mortality was less than the increase associated with population ageing between 1990 and 2017. White signifies countries and territories not experiencing an increase in deaths associated with population ageing between 1990 and 2017. The maps were drawn using the R package “maps,” which was based on the data from the Natural Earth project.